This invention relates to an improved, adjustable height fill valve for use in gravity flush toilets.
Conventional gravity flush toilets have a generally rectangular tank mounted immediately above a bowl. A water passage connects the tank and bowl through a drain outlet in the bottom of the tank. A flapper valve normally closes the drain outlet. When a user actuates the flush handle on the outside of the tank, the flapper valve is lifted and the water in the tank flows through the drain outlet into the bowl, which flushes the contents of the bowl into the sewer system. When the water level in the tank drops, the flapper valve recloses on the drain outlet and the fill valve is opened to permit refilling of the tank from a water supply line.
The typical fill valve comprises a pilot valve mounted in the tank on top of a riser which connects through an opening in the bottom of the tank to a pressurized water supply line. A float connected to the pilot valve rises and falls with the water level in the tank. When the water level falls, the pilot valve is activated and permits refilling of the tank. A portion of the water flowing through the pilot valve is diverted to an overflow tube through which the bowl is refilled to the normal standing water level therein. When the water level in the tank carries the float to a predetermined height, the pilot valve is shut off and the system is ready for the next flush.
In order to make the fill valve adaptable for the widest variety of tank sizes and shapes, its height should be adjustable. This has been done by making the riser out of two or more telescoping tubes with the pilot valve mounted on top of one of these tubes. Examples of this arrangement are found in U.S. Pat. Nos. 5,255,703 and 5,715,859. In this prior art, height adjustments are made by rotating the tubes relative to one another to disengage a locking mechanism. Once the lock is disengaged, the tubes can be moved axially to the full extent of the tubes. Once the desired height is obtained, the tubes are again rotated to re-lock them at the chosen height.
One of the disadvantages of the prior art is that the user must remember to take a positive step to re-lock the height adjustment. That is, once the locking mechanism is disengaged it remains disengaged until some positive action is taken to reengage the lock. If this reengagement step is not performed or is performed in a faulty manner, the tubes are subject to coming apart.
Another design consideration in valves of this type is the location of the float. From a space utilization standpoint it is preferable to locate the float on or about the riser. However, this can create problems in obtaining reliable valve opening when the float falls. Floats filled only with air can be too light to assure enough force to open the valve. One common way to handle this problem is to place the float on the end of an elongated arm to increase the moment about a pivot point on the valve. This has the disadvantage of greatly increasing the space required for the valve. Another approach has been to locate the float about the riser and increase its weight, and therefore its closing force, by partially filling it with water. U.S. Pat. Nos. 5,035,257, 4,600,031 and 5,287,882 are examples. The water chambers in these patents are substantially symmetrical about the riser. This arrangement is functionally adequate but can lead to manufacturing difficulties that result in a two-piece float.
Still another problem in fill valve design is how to provide anti-siphon vents. The potential for siphoning water from the tank into the water supply exists in the event of a failure of the supply line pressure during a flush sequence. To prevent contamination of the supply line, negative pressure in the supply line has to be broken by anti-siphon vents. During normal operation; however, these vents are closed off to foreclose an undesirable flow path. Conventionally these vents are located in a cap of the pilot valve which tends to increase the size of the valve.